Using the back of a large spoon or electric mixer, cream the butter until it is light. Cream in the powdered sugar, then the vanilla. Now work in the flour. Knead the dough on an unfloured board until nice and smooth. Spray the shortbread pan very lightly with a non-stick vegetable oil spray. Put the ball of dough in the middle of the pan, and working out from the center, firmly press the dough into the pan. Prick the entire surface with a fork, and bake the shortbread right in the pan at 325 degrees for about 30-35 minutes, or until it is lightly browned. Be sure that the middle is thoroughly cooked and doesn’t look slightly opaque or the shortbread might stick in the pan.

Let the shortbread cool in the pan for about 10 minutes before you loosen the edges with a knife and flip the pan over onto a wood cutting board. If the
shortbread does not come right out, hold the pan upside down over the cutting board and firmly tap one edge of the pan against the board. This should loosen
the shortbread and it should drop out. Cut the shortbread into serving pieces while it is still warm.